• Journal of the Korea Institute of Building Construction
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• v.14 no.2
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• pp.135-142
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• 2014

The heat of hydration can be reduced through the use of retarding agents. Typical retarding agents include sugar and glucose. However, these significantly delay the setting of cement paste. For the efficient use of sugar and glucose for mass concrete construction, it is necessary to develop a technique that can provide a setting behavior equivalent to that of plain concrete. In this work, the temperature rise of cement paste was monitored with the addition of various retarders including sugar and glucose. Hydrated cement powder was made with a water to cement ratio of 5 in order to accelerate the retarded cement pastes. It was found that the addition of hydrated cement powder in retarded pastes reduced the maximum temperature of cement paste. The use of hydrated cement powder could also successfully reduce the time to reach the maximum temperature.

• The Journal of the Korea Contents Association
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• v.22 no.4
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• pp.620-633
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• 2022

The purpose of this study is to examine how SMEs' perception of organizational support affects turnover intention, and to investigate the moderating effect of abusive supervisionin the relationship between organizational support perception and turnover intention. As a result of the analysis of the study, First, it was confirmed that organizational support perception had a negative (-) effect on turnover intention. Second, the higher the organizational support awareness, the lower the turnover intention, but when the abusive supervision in intervened, it was found that the organizational support perception offsets the effect that reduces the turnover intention again. That is, emotional support, turnover intention still appeared even if the abusive supervisionin was involved, but instrumental support had no effect on turnover intention when the abusive supervisionin was involved. This study is meaningful in that it expanded the scope of manufacturing services, semiconductors, and IT industries of SMEs with high turnover intentions.

• Journal of Aerospace System Engineering
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• v.16 no.6
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• pp.114-122
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• 2022

This paper explores three-dimensional unsteady computational fluid dynamic (CFD) analyses with an overset grid technique to analyse the wake effect created by a rotating propeller on a hand-launched unmanned aerial vehicle (UAV). Additionally, the influence of actual aileron deflection on the equilibrium condition of the rolling moment is examined in various hand-launched take-off conditions. The results of this study demonstrate the importance of initial aileron deflection in increasing the initial rolling stability during the hand-launched take-off process. Furthermore, an aerodynamic database is constructed to rapidly predict the aileron set values required for different take-off speeds and angle-of-attacks.

• Journal of the Korea Convergence Society
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• v.12 no.11
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• pp.391-401
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• 2021

The purpose of this study was to verify the moderating effects of the stress coping styles on the effects of internet addiction on the self-esteem of the 2030 generation during the Covid19 period. The 762 samples were selected through an online survey, and the collected data were conducted using the SPSS WIN26.0 program for frequency analysis, correlation analysis, and hierarchical regression analysis. As a result of the analysis, Internet addiction had a negative effect on self-esteem, and only seeking social support among the four sub-factors of stress response served as a moderator variable in the relationship between Internet addiction and self-esteem. Based on the results, the followings were suggested: expansion of research subjects regarding Internet addiction and interdisciplinary convergence study, providing universal provision of stress coping management programs, building a community at the local level, and discovery and reinforcing variables that offset the negative role of self-esteem of 2030 generations.

• Korean Journal of School Psychology
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• v.8 no.2
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• pp.153-173
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• 2011

In a group of 353 elementary students, the present study examined the moderation effects of prosocial behaviors and social competence in the relations between overt/relational aggression and peer status (social preference and perceived popularity). The results indicate that both overt aggression and relational aggression lowered social preference regardless of gender. Prosocial behaviors and social competence did not buffer the negative influence of aggression on social preference. Among boys, overt aggression was a significant predictor of increased perceived popularity. Although inconsistent, relational aggression also predicted boys' perceived popularity. However, among girls, relational aggression, not overt aggression, was associated with perceived popularity. The moderation effects of prosocial behaviors and social competence were significant only among boys. In other words, boys' aggression, although it lowers social preference, contributes to their social influence and dominance when it is effectively combined with positive characteristics. It is necessary to develop new intervention strategies which reflect the adaptive function of aggression within peer groups.

• Environmental and Resource Economics Review
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• v.21 no.2
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• pp.321-340
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• 2012

Korean government recently announced that new passenger cars sold within South Korea in 2009 ran an average of 12.27 kilometers per liter of fuel, which is an 7% point increase of the fuel efficiency. The government interpreted these improvements in the fuel economy as energy savings of 60,000 toe and as a reduction of 160,000 ton $CO_2$ emissions. However, improvements in energy efficiency make energy services cheaper, which is known as rebound effect. If this rebound effect exists, and the size of the effect is not negligible, ignoring this could result in overestimating the energy savings achieved by the fuel efficiency increase. Using detailed data on household and vehicle characteristics, our results suggest that there exist a short-run rebound effect of 0.299(29.9%) for the Korean automobile industry. This is notably smaller than the estimates of West (2004), which finds an estimate of 87% using cross-section data for the US. Furthermore our results highlight the importance of rebound effect on energy savings and the $CO_2$ emissions reduction. Our estimates suggest that the report from Korean government overestimates the energy savings and related $CO_2$ emissions by 29.9% point.

• Korean System Dynamics Review
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• v.12 no.2
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• pp.127-151
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• 2011

The purpose of this study is to examine measures to improve government's supply oriented housing policy in population declining cities. For this purpose, system dynamics simulation method was used to build urban-housing model and different sets of housing policies were tested to see their impact on local housing problems. Simulation result shows that there is no best set of housing policies that can solve all housing problems in population declining cities. It also indicates that housing policy that solve one type of problems can worsen other type of problems. Housing policy that increases population size has negative effect of housing oversupply. It also increases proportion of old houses in population declining cities. However, housing policy that makes city younger with newer houses tends to increase housing shortage and housing price. So, policy choice needs to be made with clear understanding of trade off between different policies. The result also shows it is difficult to expect a full scale effect of housing policy on local housing problems unless it is executed with regional economic development policy because local housing problems are so closely related with local economic problem in population declining local cities.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.14 no.5
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• pp.44-51
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• 2015

The deployment of high capacity backhaul is required due to explosive growth in mobile data services. For rapid backhaul deployment, point to point microwave is a much easier and cheaper technology. The space diversity scheme is used in point to point microwave links. The purpose of space diversity is to overcome fading by combining signals from two separate receiver antennas. For signal combining algorithm, maximum power and minimum distortion methods were used and these algorithms were reported not to be good enough for robustness in selective fading. In this paper, a more practically efficient signal combining scheme from the main and diversity branch is proposed and evaluated in selective fading channel. The proposed algorithm has shown significant performance improvement in terms of signal spectrum.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.6
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• pp.603-611
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• 2008

In this paper, we introduce a multi-coil antenna which is useful for reducing the effects of radio frequency noise in an inductively coupled RFID system. A multi-coil antenna is composed of a central coil and four subsidiary coils that are connected in series. A multi-coil antenna is designed so that the total noise disappear when the induced voltages of a central coil and subsidiary coils are added. The noise in a multi-coil antenna was about 30 dB lower than that in a single coil antenna. The multi-coil antenna is very effective in noise reduction even in an environment that the spatial distribution of RF noise is changed abruptly, and the induced noise was about 16 dB lower than that in a dual coil antenna.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.822-826
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• 2009

홍수터에 식재된 수목에 의한 운동량 교환은 흐름의 추가적인 흐름저항으로 작용한다. 따라서 수목으로 인한 통수능의 감소로 부분적인 유속 상승이 발생하기도 하지만, 전반적으로 평균유속이 감소하며 수위는 상승하게 된다. 실무적 사용목적으로 홍수터 수목의 저항은 통합 매개변수인 합성조도계수가 사용되고 있으나, 정량적인 조도계수의 추정은 매우 어려운 문제이다. 본 연구에서는 경험적으로 추정되는 비정량적 합성조도 계수의 한계를 극복하고, 실무적으로 사용이 용이하도록 수목에 의한 흐름저항 항을 분리한 1차원 상류이송 음해기법이 개발되었다. 개발된 기법의 평가를 위하여 균일한 단면에서 수행된 수리실험에 적용하였으며, 다양한 유량규모 및 식재조건에서 제안된 기법의 적용성 및 정확성을 확인하였다. 불규칙한 단면형상을 가진 실제 하천의 홍수터에 식재된 수목군의 경우를 가정하여 1/25 정상축척의 수리실험을 실시하였고, 100년 빈도 홍수량에서 수목식재 전후의 실측결과를 개발된 수치기법으로 계산하여 비교하였다. 개발된 기법은 모든 경우에서 사용자의 주관적인 판단 없이 정확하면서 안정적인 해를 제공하였으므로, 흐름의 2차원 효과가 상쇄될 수 있는 광폭의 자연하천에서 수목의 식재기준 분석을 위한 대안으로 사용될 수 있을 것이다.